Deep trench surrounded MOSFET with planar MOS gate

Abstract

Apparatus and other embodiments associated with high speed and high breakdown voltage MOS rectifier are disclosed. A Junction All Around structure, where a deep trench structure surrounds and encloses a P-N junction or a MOS structure, is created and applied in various rectifiers. In one embodiment, multiple deep trenches in concentric ring circles enclosed several horizontal P-N junctions in concentric ring circles. In another embodiment, an enclosed deep trench in ring circle surrounds a horizontal P-N junction, which results in a planar N-channel MOS during forward bias. This structure can be extended to multiple deep trenches with associated horizontal P-N junctions.

What is claimed is: 
     
       1. A MOSFET, comprising:
 a first n-type semiconductor layer; 
 a second n-type epitaxial semiconductor layer with lower doping concentration but larger depth than that of the first n-type semiconductor layer, deposed on top of the first n-type semiconductor layer; 
 a p-type semiconductor layer deposed on the top surface of the second n-type semiconductor layer; 
 a metal layer deposed above the p-type semiconductor layer; 
 at least two enclosed operating deep trenches in concentric continuous ring circles 
 comprising a first deep trench and a second deep trench, wherein
 the first operating deep trench etched from the top of the p-type semiconductor layer down to the interface of the first n-type semiconductor layer and the second n-type semiconductor layer; 
 the second operating deep trench etched from the top of the p-type semiconductor layer down to the interface of the first n-type semiconductor layer and the second n-type semiconductor layer, and the first operating deep trench has smaller radius than the second operating deep trench; 
 
 a first set of two third n-type semiconductor in continuous ring circles deposed in the upper part of the p-type semiconductor layer and being adjacent to both inner-side and outer-side of the first enclosed deep trench but not in direct contact with the first enclosed deep trench; and 
 a second set of two third n-type semiconductor in continuous ring circles deposed in the upper part of the p-type semiconductor layer and being adjacent to both inner-side and outer-side of the second enclosed deep trench but not in direct contact with the second enclosed deep trench. 
 
     
     
       2. The MOSFET device of  claim 1 , wherein the at least two enclosed operating deep trenches have oxide coating on their sidewalls and bottom surfaces, and a polysilicon layer filling their centers and connected to the metal layer for operation to form a MOS-Sidewall-Plate structure. 
     
     
       3. The MOSFET device of  claim 1 , wherein the first-set outer-side third n-type semiconductor ring circle, which has smaller radius than that of the second-set inner-side third n-type semiconductor ring circle, is spaced apart from the second-set inner-side third n-type semiconductor ring circle, such that leaving the p-type semiconductor in between. 
     
     
       4. The MOSFET device of  claim 1 , further comprising a third enclosed operating deep trench in concentric continuous ring etched from the top of the p-type semiconductor layer down to the interface of the first n-type semiconductor layer and the second-type semiconductor layer, wherein the third operating deep trench is between the first operating deep trench and second operating deep trench with substantially the same distance to both the first operating deep trench and second operating deep trench. 
     
     
       5. The MOSFET device of  claim 1 , further comprising an enclosed non-operating deep trench in concentric ring circle filled with only oxide and located as the outermost ring circle of the device. 
     
     
       6. The MOSFET device of  claim 4 , further comprising a third set of two third n-type semiconductor in continuous ring circles deposed in the upper part of the p-type semiconductor layer and being adjacent to both inner-side and outer-side of the third enclosed deep trench but not in direct contact with the third enclosed deep trench. 
     
     
       7. The MOSFET device of  claim 5 , wherein the enclosed non-operating deep trench in concentric ring circle is the outermost deep trench of the MOSFET device. 
     
     
       8. The MOSFET device of  claim 7 , wherein all deep trenches except the outermost deep trench are operating trenches having MOS-Sidewall-Plate structure and in concentric continuous ring circles. 
     
     
       9. The MOSFET device of  claim 1 , wherein the first and second operating deep trenches extend into the first n-type semiconductor layer. 
     
     
       10. The MOSFET device of  claim 1 , further comprising a planar electrode deposed above the metal layer and between the first and the second enclosed deep trenches.